1. Field of the Invention
The present invention relates to a multilayer, cold deformable composite metal article capable of being deep drawn. It also relates to a cooking utensil, produced from such a composite metal article.
2. Description of the Prior Art
Such a composite article consisting of a plurality of layers connected to each other must feature, depending on the final product to which it is worked, a large variety of differing properties. The properties of the individual layers are, thereby, combined in an ideal way. It is thereby by all means possible that certain properties, e.g. deforming properties of a multilayer article are substantially different from the deforming properties, which could be expected from every single material of the individual layers.
There are now applications, which demand a composite article which is not only capable of being cold deformed and deep drawn, but which is also heat conductive and magnetizable.
An example of an application of such a multilayer composite article can be a multilayer, deep drawn cooking utensil having a bottom portion and a wall portion formed integrally with the bottom portion, whereby the structure of the cross section of the bottom portion is the same as the structure of the cross section of the side wall portion.
Such cooking utensils should lend themselves to be used with traditional energy sources such as gas, electricity or halogen, but also specifically on induction ranges.
The multilayer composite article, from which such a cooking utensil is produced, must have good heat conducting properties and at the same time must be magnetizable. Furthermore at least the raw material article made as a composite article must be capable of being deep drawn for the production of such a cooking utensil.
Known cooking utensils which have been deep drawn from known multilayer composite layers feature on the one hand an inferior long-term behavior specifically of the bottom portion, in that deformations occur, i.e. the utensil supporting surface of the bottom portion deforms after a prolonged use. On the other hand and specifically the production suffers from a large number of rejects, scrap. When, for instance, such composite articles are deep drawn, re-drawn and re-pressed, the individual layers, which originally have been bound together, detach themselves from each other and/or tear, and specifically when deforming ferritic stainless steels by 90.degree. relative to the direction of rolling, zones of reduction or contraction occur, which look like grooves or waves, a symptom which in the art is called fluted and necessitates by at least one further production step a grinding of the product. Other multilayer composite articles do not lend themselves to the same deforming ratios.